Electronic Design |

Ideation & sketches

The main component of the actuator responsible for selecting the different heddles of the loom is an electromagnet that attracts or repels the actuator.

Basic unit electromagnet

The problem with using a single electromagnet is that it required a signal and two transistors to change the state of each electromagnet, with two electromagnets needed per thread, which meant that for each thread, two signals and four transistors were necessary. For this reason, I decided that instead of using single electromagnets, I would use an arrangement of two electromagnets.

The advantage of two electromagnets is that when current passes through both and they are aligned with the coils in opposite directions, the magnetic charge of each magnet is reversed, achieving the desired effect to reverse the direction of the actuator that selects the loom's meshes.

Final electromagnets design

Once the configuration of the electromagnets was selected, it was time to design the circuit that would control the direction of the current, which would cause the change in the magnetic field of the electromagnets responsible for the state change in the actuators. For this, I decided to use the same configuration of an H-bridge.

An H-bridge is an electronic circuit that switches the polarity of a voltage applied to a load. These circuits are often used in robotics and other applications to allow DC motors to run forwards or backwards.

Traditional H Bridge configuration

In the H-bridge configuration, there are 4 diodes. The H-bridge, being designed for motor movement, has the possibility that the motor, once the current is stopped, either changes direction or generates current between its terminals. This current can return to the system, which is why those 4 diodes exist, to prevent a short circuit from the current generated by the moving motor.

By conducting tests, I determined that the risk of generating a reverse current caused by the charging and discharging of the electromagnets is negligible. For this reason, I omitted the diodes from the H-bridge. Additionally, this helped me with the space required to solder the components onto the boards.

Loom One H Bridge configuration

Once the circuit was determined, I decided to simulate it using the Multisim program. I built the circuit with the transistors that change the state of the mesh and with the help of a virtual oscilloscope, I was able to verify that the direction of the current changes due to the change in polarity of the circuit.

All of this is controlled by two gates that simulate the signal from the microprocessors that control the actuators.

In the video, we can see the circuit simulation, with which I test its proper functioning.

Once the control concept was tested, I decided to make the board to actuate each of the actuators guided by a signal from the slave microcontroller that is directly connected to the board.

Let's remember that in this iteration each card covers 4 cm and has 4 threads per centimeter. Since it is still a prototype, each controller measures 1 cm, so to have 4 threads per centimeter, it is necessary to stagger each of the actuators every 2.5 mm.

Actuators ladder configuration

The control electronic board for each of the actuators that select the meshes was made with an online program called Easy EDA and follows the same configuration as the solid on which the actuators are mounted. The holes visible on the board are for the heddles that hold the wires to pass through.

PCB Design

If we make a closeup to the board design you can clearly recognize the H bridge configuration of the board.

PCB H Bridge Design

By the way, I triple checked the board design and the moment I made this close up, I saw a mistake. -Can you spot it? :(

The electronic control card for each of the actuators that select the meshes is connected to two slave circuits that will be controlled from a master as indicated in the software section on this page.

I decided that the slave cards would be controlled with an Arduino Nano board, as it had enough control pins to manage 8 wires (16 ports) plus the power and I2C communication pins. These cards were also designed in EasyEDA.

PCB H Bridge Design

Once the boards are designed with EasyEDA, the integration with the JLCPCB factory in China, which manufactures them professionally in just a week and a half.

The design of the Gerber files can be seen in the following images:

Fabrication file for Loom One controler

Fabrication file for slave board

It is worth mentioning that when I sent the cards to be made, I had a problem because the design of the card's print interfered with the cutting layer. I must thank Adrian Torres from Fab Lab León for helping me solve the problem and lending a hand to review the card.

Friday I received the PCB boards and all the components from Mouser. They turned out beautiful!

Finally, the child are home

I designed the board with very small components due to the size and the amount of them that I had to insert on the board.

Ini mini miny components

I am not very good in soldering the components, and my eyesight is not what it used to be. But for every great task there is a great solution, so I prepare myself and got to work.

Ready to fulfill The Task!

I just soldered two actuators and two slave board to test the components and communication between them. I think I did a pretty GOOD JOB!

Finally Loom One PCB is ready to test

Also the slave boards are ready!

Arduino nano slave boards

Next Steps

I will check if the board is functioning properly and if it has any issue with the actuators before the system integration.